Field of the Invention
This invention relates to polymer filter assemblies as used to process/filter a flowable material used to extrusion form sheet layers/products.
Background Art
One basic extrusion sheet forming system utilizes the combination of a barrel assembly, a polymer filter assembly, and a die assembly through which flowable material is delivered from a supply to a processing/roll system through which one or more sheet layers are formed. An exemplary system is shown in U.S. Pat. No. 8,021,140. Flowable material from the supply is delivered through the barrel assembly to the polymer filter assembly, within which filtering of the flowable material takes place. From the polymer filter assembly, the filtered flowable material is directed to the die assembly, which causes a controlled delivery of the flowable material to a processing/roll system upon which the flowable material is solidified and formed into a sheet layer. The sheet layer may be accumulated by itself or united with one or more additional sheet layers to produce a completed product, or an intermediate product that is further processed downstream, or elsewhere.
The polymer filter assembly consists of a frame with contained processing components that collectively may weigh several tons. The polymer filter assembly is operatively engaged with the barrel assembly and die assembly through cooperating connectors that are configured to maintain a precise alignment that is necessary for optimal system performance.
Typically, the cooperating assemblies and connectors therebetween are designed and manufactured with close tolerances. It is difficult with components having large masses and weights, typical for extruding systems, to precisely establish and maintain an intended alignment. This problem is aggravated by the fact that with the system in use, the flowable material is at working temperatures high enough that the components significantly thermally expand and contract. This phenomenon is particularly significant given the different thicknesses and configurations of parts.
In the absence of some accommodation for these conditions, deformation and skewing of parts relationships could compromise the integrity of sheets and products generated. Various modifications have been made to such systems in the past to address these problems.
It is known, for example, to mount a polymer filter assembly by bolting it fixedly to the barrel system without any additional support. It is also known to support a polymer filter on a wheeled cart placed against a horizontal base surface. Both of these designs create out-of-plane loads that are transmitted between cooperating components both upstream and downstream of the polymer filter assembly. Further, these designs do not maintain a precise required alignment between the polymer filter assembly and cooperating upstream and downstream components, nor do they support the weight of the components when a misalignment naturally occurs.
The industry continues to seek designs that better accommodate thermal deformations and potential component misalignment caused by thermally induced dimensional variations and other conditions.